1. Field of Invention
The invention relates to an image processing system and the method of the same. In particular, the invention relates to an error-diffusion image processing method that employs block reading to convert a multi-level image to a bi-level image for output and the method thereof.
2. Related Art
The multi-level image generally refers to a digital image created by a digital camera, scanner, or computer software. In a monochrome image, each pixel consists of at least two different levels of gray. In a color image, there are many different color planes. Each pixel consists of at least two different levels in each color plane.
Either monochrome or color images are usually output via a printer or a display device. However, these output devices often describe these multi-level images in a bi-level way. For example, a monochrome image can only be described using black-level and white-level. For a color image, each color plane is described using on-level and off-level. Therefore, before a multi-level image is sent to these output devices for output, it has to be converted into a bi-level image first.
Such a process of converting a multi-level image into a bi-level image is also called halftoning. The error-diffusion image processing is a widely used conventional halftoning technique. However, the conventional error-diffusion image processing is performed by row reading. That is, the operation is not performed until a whole row of image data are read in. Therefore, it takes a lot of memory space to store the image data. The operation efficiency is also lowered because of the frequent access of data in the memory.
Since the cost of memory is not cheap and the memory space available in the output devices is limited, the conventional error-diffusion image processing method for converting multi-level images to bi-level images indeed faces the problems of memory space usage and the operation efficiency. Therefore, it is necessary to provide an improved solution to solve these problems.